[unreadable] Efficiency of hemodialysis is currently limited by dialyzer technology. Although new membranes with large surface areas have been developed, the increase in delivered treatment is only marginal. Double dialyzer therapies have been shown to be superior to standard high efficiency/ high flux dialysis treatments; however implementation of double dialyzer therapies has been limited by the complexity of the dialysis treatment setup. It is proposed to develop a double fiber bundle dialyzer in a single casing that optimizes diffusive and convective removal of solutes. In series double dialyzer dialysis will be evaluated in-vitro as both the flux and surface area of dialyzers are altered. Clearance of urea, creatinine and Vit B12 will be measured. Filtration in each dialyzer will be assessed to evaluate filtration fractions. Ultimately, the ideal combination(s) of dialyzer size and flux will be derived. This combination(s) will then be applied to a single casing double fiber bundle prototype. This prototype will be evaluated for clearance and filtration characteristics. The limits of the system will be based on dialysis machine operating parameters (i.e. pressures and flows). This double fiber dialyzer will be applicable to all existing dialysis equipment, therefore easily adapted by the dialysis community. This product will provide a dialysis therapy that clearly surpasses existing dialysis efficiencies, applicable to the more than 300,000 dialysis patients in the US and 1 million patients worldwide. A future partnership with a large dialysis equipment manufacturer is one possible route to market. A company such as Baxter Healthcare both manufactures and distributes hemodialyzers throughout the world. Contract manufacturing the dialyzer and distributing via distribution companies or licensing the technology for others to manufacture and distribute are two alternative routes to be evaluated. [unreadable] [unreadable] [unreadable]